Variable rate stepper motor driver circuit and method

Abstract

A circuit inserted between a microprocessor controller and a stepper motor driver uses a detector to detect single peak or double peak pulses from the controller and selectively produce one or two motor steps for each controller program loop, and a time delay circuit to regulate the time of the second step to yield a substantially regular stepping rate.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A variable rate stepper motor driver circuit responsive to a coded input signal for issuing output pulses at a low rate or a higher rate comprising: a motor driver circuit responsive to an input signal for delivering an output signal for stepping a motor at each input signal, and   a decoding circuit responsive to the coded input signal for detecting a higher rate code and issuing at least one auxiliary input signal to the driver circuit when a higher rate code is detected to step the motor at least a second time.   
     
     
       2. A variable rate stepper motor driver circuit responsive to a coded input signal for issuing output pulses at a low rate or a higher rate comprising: a motor driver circuit responsive to an input signal for delivering an output signal for stepping a motor at each input signal,   a decoding circuit responsive to the coded input signal for detecting a higher rate code, and   timing means subject to the decoding circuit and effective when a high rate code is detected for issuing at least one auxiliary input signal to the driver circuit at preset times after the coded input signal to step the motor at least a second time.   
     
     
       3. A dual rate stepper motor driver circuit responsive to a coded input signal for issuing output pulses at a low rate or a high rate comprising: a motor driver circuit responsive to an input signal for delivering an output signal for stepping a motor at each input signal,   a decoding circuit responsive to the coded input signal for detecting a high rate code and issuing a high rate signal,   a timing circuit for issuing a time signal at a delayed time after the coded input signal, and   means for supplying an auxiliary input signal to the motor driver circuit when both the high rate signal and the time signal are present.   
     
     
       4. A stepper motor control for operating a stepper motor at a first rate or a second rate which is double the first rate, comprising: means for issuing single pulses at a first rate when stepper motor operation at the first rate is desired and for issuing double pulses at the same rate when stepper motor operation at the second rate is desired,   motor driving means having an input coupled to the control means for immediately stepping the motor once when either a single pulse or a double pulse is received, and   means responsive to a double pulse and coupled to the input of the motor driving means for generating a single pulse after the motor has completed one step to step the motor a second time.   
     
     
       5. A stepper motor control for operating a stepper motor at a first rate or a second rate which is double the first rate, comprising: control means for issuing single pulses at a first rate when stepper motor operation at the first rate is desired and for issuing double pulses at the same rate when stepper motor operation at the second rate is desired,   motor driving means having an input coupled to the control means for immediately stepping the motor once when either a single pulse or a double pulse is received,   a detector circuit for detecting the occurrence of a double pulse, and   a timer circuit connected to the detector circuit and coupled to the input of the motor driving means for generating a single pulse to step the motor a fixed time after a double pulse is issued.   
     
     
       6. The invention as defined in claim 5 wherein the timer circuit is set to generate said single pulse approximately midway between the pulses issued by the control means to effectively maintain a regular stepper motor rate when the second rate is in effect. 
     
     
       7. The method of controlling the rate of a stepper motor by a coded signal comprising the steps of: producing a coded signal at a fixed repetition rate for initiating stepper motor operation, the rate of operation depending on the signal repetition rate and on the code,   stepping the motor once when the coded signal is produced,   decoding the signal to determine the number of motor steps for each signal produced, and   before another signal is produced, stepping the motor again for each additional step required by the code.   
     
     
       8. The invention as defined in claim 7 including timing each additional step of the motor to yield a substantially regular stepping rate. 
     
     
       9. The method of controlling the rate of a stepper motor by a coded signal comprising the steps of: producing a periodic coded signal at a fixed repetition rate for initiating stepper motor operation, the signal comprising a single pulse for a single motor step in each period and a double pulse for two motor steps in each period,   stepping the motor once when the coded signal is produced,   detecting the presence of a double pulse, and   delaying for substantially half a period and then stepping the motor again if a double pulse is detected.